Phosphorescent Iridium Complexes:Design,Synthesis,Photophysical Properties And Applications In Metal Cation Sensing

Metal ions play an important role in various physiological activities.Therefore,in order to clearly understand the mechanism of metal ions in the body,real-time dynamic labeling and position tracking are required.But most of fluorescent probes are insufficient,such as photobleaching,short fluorescence lifetime,and low quantum efficiency.Phosphorescent transition metal complexes have numerous excellent photophysical properties,such as long phosphorescence emission lifetime,great light stability,easy-tunable emission wavelength,and high quantum efficiency.We aimed at combining the metal ion detection group and phosphorescent metal iridium???complex to exert the advantages of transition metal complex,and the fluorescent probe Ir?pqu?2OC for detecting iron ions is designed and synthesized.In addition,we have changed the intrinsic synthesis of traditional iridium???complexes,introduced a new cyclometalated ligand and synthesized the corresponding mixed-ligand m-Cl-bridged dimer complexes.Splitting of the mixed-ligand dimer and introduction of an ancillary ligand provided access to a new type of tris-heteroleptic complexes.The novel iridium???complex with three different ligands will compare with the traditional structure of the complex to study their photophysical properties and possible applications in future.The main contents are as follows:Firstly,coumarin-based part was designed and synthesized as the metal ion-binding group because of its good biological compatibility,and 2-phenylquinoline was used as the main ligand of the iridium???complex Ir?pqu?₂OC.As an iron???ion probe,it exhibits both excellent photophysical properties of the iridium???complex and high selectivity to Fe³⁺.When the probe combine with iron ions,the absorption intensity increases as the concentration of iron ions increases and the emission intensity drop significantly with the emission lifetime has also decreased significantly.Other metal ions do not perform this phenomenon,so the probe can be used as specific detection of Fe3+.The coumarin-based structure and low toxicity of the probe also gives it an advantage in cell imaging.Then we designed and synthesized the tris-heteroleptic complexes with thiophene-quinoline and ppy-C4 as cyclometalated ligands using a new synthetic method reported in recent years.The complexes are all emitting in the orange-red region.This new method changes when synthesizing m-Cl-dimers compared to complexes synthesized by conventional methods.By adding two different cyclometalated ligands,several mixed dimers were obtained and then acetylacetone was added to synthesize a less stable complex.Using the difference in polarity,the iridium???complexes with three different ligands which comprise acetylacetone as an ancillary ligand was isolated and purified.The acetylacetone fraction is removed by acid hydrolysis,and the pure dimeric Ir???precursor is combined with another ancillary ligand to obtain the target product.We mainly analyze the difference in photophysical properties between tris-heteroleptic complexes and traditional complexes,and provide a feasible way to obtain more efficient iridium???complexes emitting in orange-red region.